Use of Stable Carbon and Nitrogen Isotopes to Trace Natural and Anthropogenic Inputs into Riverine Systems in the Athabasca Oil Sands Region

Stable isotopes of carbon and nitrogen in fish were examined as a potential tracer of exposure to oil sands constituents in naturally eroded environments and in areas of anthropogenic activity (municipal and industrial effluent discharges; oil sands surface mining) within the Athabasca River drainage basin of northern Alberta, Canada. Longnose sucker (Catostomus catostomus), trout-perch (Percopsis omiscomaycus), and slimy sculpin (Cottus cognatus) showed changes in delta(13)C values with the river gradient. Site-specific differences in the delta(13)C values of fish were more pronounced for the small-bodied fish species in the lower reaches of a tributary (slimy sculpin) and immediately downstream of tributary inputs along the Athabasca River (trout-perch), where potential exposure to the oil sands constituents is elevated. There were also species and site-specific trends for delta(15)N values. Site-specific trends attributed to municipal or industrial effluent discharge or tributary inputs may prove to be a useful tool for defining residency on the oil sands deposit. This study has provided baseline data of isotope values for fish species which are currently used (longnose sucker) or may be used in future environmental effects monitoring programs. Defining residency and exposure to the oil sands deposit is critical to establishing exposure-response relationships, particularly since there are new expansions to oil sands mining operations.